JP2017068900A - Carboxymethyl cellulose or salt thereof for nonaqueous electrolyte secondary battery separator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a carboxymethyl cellulose or a salt thereof for a nonaqueous electrolyte secondary battery, which never causes the reduction in capacity even if it suffers the iteration of charge and discharge; a coating liquid for a nonaqueous electrolyte secondary battery separator, which contains such carboxymethyl cellulose; and a nonaqueous electrolyte secondary battery separator including the coating liquid.SOLUTION: A carboxymethyl cellulose or salt thereof (CMC) is used as a water-soluble dispersant for a nonaqueous electrolyte secondary battery separator. The CMC is less than 50 μm in volume-based 100%-cumulative total of particle diameters (in a methanol dispersant). Supposing that the CMC of a dry mass B is dissolved in 2 liters of 0.3 mass% aqueous solution and filtered by a filter (in a reduced pressure condition of -200 mmHg with a 250-mesh) and thus a dry mass A of the residue on the filter is measured, the proportion of the dry mass A to the dry mass B for the CMC is less than 50 ppm.SELECTED DRAWING: None

Description

  The present invention relates to carboxymethyl cellulose for a non-aqueous electrolyte secondary battery separator or a salt thereof, a coating solution for a non-aqueous electrolyte secondary battery separator containing the same, and a non-aqueous electrolyte secondary battery separator containing the same.

  Non-aqueous electrolyte secondary batteries are used not only in small devices such as mobile phones, portable music players, and notebook personal computers, but also in large devices such as electric bicycles, hybrid vehicles, and electric vehicles. Yes. For this reason, non-aqueous electrolyte secondary batteries are required to have high capacity and performance such as charge / discharge characteristics at a large current, but non-aqueous electrolyte secondary batteries emit smoke, ignite, It is known that there is a high risk of rupture and the like, and improvement in safety is also required.

  In response to this requirement, Patent Document 1 discloses a coating liquid containing insulating fine particles having heat resistance, a thickener, and a dispersion medium, and a separator coated with the coating liquid on a substrate. Although proposed, since the stability of the coating solution is not sufficient, the disclosed nonaqueous electrolyte secondary battery has a problem such as a decrease in capacity while it is repeatedly charged and discharged.

  On the other hand, Patent Document 2 discloses an alumina hydrate, an aqueous dispersion of a binder polymer, a CMC salt having a viscosity of 100 mPa · sec to 500 mPa · sec at 25 ° C. of a 1% by mass aqueous solution, 1% by mass. The nonaqueous electrolyte secondary battery can be prevented from being reduced in capacity due to charge and discharge by using a coating solution for nonaqueous electrolyte secondary battery having a CMC salt with an aqueous solution viscosity at 25 ° C. of 3000 mPa · sec to 10000 mPa · sec. Is held.

International Publication No. 2009/096451 JP2013-115031A

  However, the non-aqueous electrolyte secondary battery using the non-aqueous electrolyte secondary battery coating solution described in Patent Document 3 can suppress the capacity reduction due to charge and discharge more than the conventional non-aqueous electrolyte secondary battery. There is a need for improvement.

  Therefore, the present invention contains carboxymethyl cellulose or a salt thereof for a non-aqueous electrolyte secondary battery that has a small capacity drop even after repeated charge and discharge, a coating solution for a non-aqueous electrolyte secondary battery separator containing the same, and the same An object is to provide a nonaqueous electrolyte secondary battery separator.

The present invention provides the following [1] to [5].
[1] Carboxymethylcellulose or a salt thereof used as a water-soluble dispersant for a nonaqueous electrolyte secondary battery separator, the volume measured with a laser diffraction / scattering particle size distribution meter using methanol of the carboxymethylcellulose as a dispersion medium A cumulative 100% particle diameter is less than 50 μm, and 2 liters of a 0.3% by weight aqueous solution of the carboxymethylcellulose or a salt thereof having a dry weight of B is prepared and filtered through a 250 mesh filter under a reduced pressure of −200 mmHg. Carboxymethylcellulose or a salt thereof, wherein the ratio of the dry mass A to the dry mass B is less than 50 ppm when the dry mass A of the residue on the filter after filtration is measured.
[2] A coating solution for a non-aqueous electrolyte secondary battery separator containing the carboxymethyl cellulose or a salt thereof, alumina hydrate, and a water-dispersible resin described in [1].
[3] A coating solution for a non-aqueous electrolyte secondary battery separator containing the carboxymethyl cellulose or a salt thereof according to [1], an alumina hydrate, a water-dispersible resin, and a thickener.
[4] The thickener is carboxymethylcellulose or a salt thereof, and a volume cumulative 100% particle diameter measured by a laser diffraction / scattering particle size distribution meter using methanol of the carboxymethylcellulose as a dispersion medium is less than 50 μm, 2 liters of a 0.3% by weight aqueous solution of the carboxymethylcellulose or a salt thereof having a dry weight of B is prepared and filtered through a 250 mesh filter under a reduced pressure of −200 mmHg, and the dry weight of the residue on the filter after filtration The nonaqueous electrolyte secondary battery separator coating solution according to [3], wherein, when A is measured, the ratio of the dry mass A to the dry mass B is less than 50 ppm.
[5] A lithium ion battery separator, wherein the coating liquid according to any one of [2] to [4] is applied to a nonwoven fabric and dried.

  According to the present invention, carboxymethyl cellulose or a salt thereof for a non-aqueous electrolyte secondary battery with little reduction in capacity even after repeated charge and discharge, a coating solution for a non-aqueous electrolyte secondary battery separator containing the same, and the same A nonaqueous electrolyte secondary battery separator can be provided.

(Water-soluble dispersant, thickener: carboxymethyl cellulose or a salt thereof)
Carboxymethylcellulose or a salt thereof (hereinafter sometimes abbreviated as “CMC”) used as a water-soluble dispersant and thickener for the non-aqueous electrolyte secondary battery separator of the present invention uses CMC methanol as a dispersion medium. A volume cumulative 100% particle size measured by a laser diffraction / scattering particle size distribution meter is less than 50 μm, and 2 liters of a 0.3% by weight aqueous solution of CMC having a dry weight of B is prepared, and 250 at a reduced pressure of −200 mmHg. When all are filtered with a mesh filter and the dry mass A of the residue on the filter after filtration is measured, the ratio of the dry mass A to the dry mass B is less than 50 ppm.

  By using CMC under the above conditions for the coating solution for a non-aqueous electrolyte secondary battery separator, the amount of CMC undissolved material in this coating solution can be greatly reduced. For this reason, in the non-aqueous electrolyte secondary battery separator manufactured by applying this coating liquid to a nonwoven fabric and drying, the occurrence of streak-like defects (streaks) on the surface can be greatly suppressed. In addition, if there is an undissolved material, the undissolved material shrinks and pinholes are generated in the drying step after coating, but this problem can be prevented by using the CMC with less undissolved material of the present invention.

  Normally, the coating solution for the non-aqueous electrolyte secondary battery separator is subjected to filter treatment before coating. Although this process can remove hard foreign matters such as metal, it is soft such as undissolved CMC. When the polymer is pressurized (back pressure) during the filtering process, it deforms and passes through the filter, so that it is difficult to remove the polymer. In addition, when CMC in which a large amount of undissolved material is generated is filtered, there is a problem that the filter is easily clogged and the removal efficiency of the undissolved material is significantly reduced.

  The CMC for a non-aqueous electrolyte secondary battery separator of the present invention has a structure in which a hydroxyl group in a glucose residue constituting cellulose is substituted with a carboxymethyl ether group. Examples of CMC salts include CMC sodium salt, CMC lithium salt, and the like.

  The degree of carboxymethyl substitution (DS) per anhydroglucose unit of CMC for the non-aqueous electrolyte secondary battery separator of the present invention is preferably 0.45 to 1.5, and preferably 0.6 to 1.5. More preferably, it is 0.6-1.0. If the degree of carboxymethyl substitution is less than 0.45, there is a possibility that dissolution in water may not be sufficient. The anhydroglucose unit means an individual anhydroglucose constituting cellulose, and the degree of carboxymethyl substitution means the ratio of the hydroxyl groups in the glucose residues constituting cellulose that are substituted with carboxymethyl ether groups. Indicates.

  The degree of carboxymethyl substitution can be confirmed by measuring the amount of base such as sodium hydroxide required to neutralize CMC in the sample. In the measurement of the salt of CMC, after converting it to CMC (H type) in advance, it is measured by appropriately combining an indicator such as back titration with a base and an acid, phenolphthalein and the like.

  The viscosity of a 1% by weight aqueous solution of a CMC (water-soluble dispersant) for a non-aqueous electrolyte secondary battery separator of the present invention measured with a B-type viscometer at 25 ° C. is preferably 100 to 20,000 mPa · s. 100 to 500 mPa · s is more preferable.

  The viscosity of a 1% by weight aqueous solution of the CMC (thickener) for the nonaqueous electrolyte secondary battery separator of the present invention measured with a B-type viscometer at 25 ° C. is preferably 100 to 20,000 mPa · s, The thing of 1,000-10,000 mPa * s is more preferable.

  In this invention, the manufacturing method of CMC is not limited, For example, after processing the cellulose which is a raw material with an alkali and preparing an alkali cellulose, it can manufacture by adding an etherifying agent and making it etherify.

  The cellulose as the raw material can be used without any particular limitation, but those having high cellulose purity are preferred, and examples thereof include dissolved pulp and linter.

  As the alkalinizing agent, an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide can be used. As the etherifying agent, monochloroacetic acid, sodium monochloroacetate or the like can be used.

  The method for producing water-soluble CMC is not particularly limited, but the molar ratio of the alkalizing agent to the etherifying agent is about 2.00 to 2.45 when monochloroacetic acid is used as the etherifying agent.

  The CMC for the non-aqueous electrolyte secondary battery separator of the present invention has been subjected to pulverization treatment. The pulverization method includes a dry pulverization method in which the powder is processed, and a dispersion or dissolution in a liquid. Both the wet pulverization method of processing in a wet state is exemplified. Any of these may be selected in the present invention.

  Examples of the pulverizer that can be used for the mechanical pulverization treatment in the present invention include the following dry pulverizers and wet pulverizers.

  Examples of the dry pulverizer include a cutting mill, an impact mill, an airflow mill, and a medium mill. These can be used alone or in combination, and can be further processed in several stages with the same model, but an airflow mill is preferred. Cutting mills include mesh mill (manufactured by Horai Co., Ltd.), Atoms (manufactured by Hyakuma Yamamoto Co., Ltd.), knife mill (manufactured by Pulman), granulator (manufactured by Herbolt), rotary cutter mill (Nara Co., Ltd.) Examples thereof are manufactured by Machine Works). As impact mills, Pulperizer (manufactured by Hosokawa Micron Corporation), Fine Ipact Mill (manufactured by Hosokawa Micron Corporation), Super Micron Mill (manufactured by Hosokawa Micron Corporation), Sample Mill (manufactured by Seisin Co., Ltd.), Bantam Mill ( Examples thereof include Seisin Co., Ltd., Atomizer (manufactured by Seisin Co., Ltd.), Tornado Mill (Nikkiso Co., Ltd.), Turbo Mill (Turbo Industry Co., Ltd.), Bevel Impactor (Aikawa Tekko Co., Ltd.), and the like. As the airflow mill, CGS type jet mill (manufactured by Mitsui Mining Co., Ltd.), jet mill (manufactured by Sanjo Industry Co., Ltd.), Ebara Jet Micronizer (manufactured by Ebara Corporation), Selenium Miller (Masuyuki Sangyo) And a supersonic jet mill (manufactured by Nippon Pneumatic Industry Co., Ltd.). Examples of the medium mill include a vibration ball mill. Examples of the wet pulverizer include a mass collider (manufactured by Masuko Sangyo Co., Ltd.), a high-pressure homogenizer (manufactured by Sanmaru Machinery Co., Ltd.), and a media mill. Examples of the medium mill include a bead mill (manufactured by IMEX Co., Ltd.).

  The particle size of CMC for the non-aqueous electrolyte secondary battery separator of the present invention is a value of 100% cumulative volume particle size measured by a laser diffraction / scattering particle size distribution meter using methanol as a dispersant (hereinafter referred to as “maximum particle size”). Is preferably 5 to 50 μm, and more preferably 5 to 45 μm. When the maximum particle size of carboxymethyl cellulose or a salt thereof is 50 μm or more, undissolved substances in the aqueous solution of carboxymethyl cellulose or a salt thereof tend to increase.

  In the present invention, the CMC having the maximum particle size of 5 to 50 μm can be granulated and used. In addition, when granulated, the maximum particle size of the granulated product may be 50 μm or more. I do not care.

  The CMC for the non-aqueous electrolyte secondary battery separator of the present invention is preferably subjected to a classification treatment so that the maximum particle size is less than 50 μm. The classification time is not particularly limited, and may be provided during the pulverization process or after the pulverization process is completed. As a classification method, a known method such as a method using a dry classifier or a wet classifier may be used. Examples of the dry classifier include a cyclone classifier, a DS separator, a turbo classifier, a micro separator, and an air separator. On the other hand, examples of the wet classifier include a hydrocyclone classifier, a centrifugal settling machine, and a hydrosilator. Of these, a dry classifier is preferable, and a cyclone classifier is more preferable.

(Coating solution for non-aqueous electrolyte secondary battery separator)
The coating solution for a non-aqueous electrolyte secondary battery separator of the present invention essentially comprises the above-mentioned water-soluble dispersant (CMC that defines the amount of undissolved material), alumina hydrate, and water-dispersible resin. The thickener is added.

  The addition amount of the water-soluble dispersant (CMC defining the amount of undissolved material) is preferably 0.05% by mass or more and 3.00% by mass or less, and 0.10% by mass or more and 2.00% by mass with respect to the alumina hydrate. % Or less is more preferable. When the amount of the CMC salt used as the aqueous dispersant is too small, the alumina hydrate may aggregate when the CMC salt used as the thickener is added. When the amount of the CMC salt used as the aqueous dispersant is too large, the high rate charge / discharge characteristics may be deteriorated.

  The amount of CMC used as a thickener is preferably 0.05% by mass or more and 3.00% by mass or less, and more preferably 0.10% by mass or more and 2.00% by mass or less with respect to the alumina hydrate. When the addition amount of the CMC salt used as the thickener is too small, the coating liquid may penetrate the opposite surface of the nonwoven fabric or the stability of the coating liquid may be reduced. If the amount of the CMC salt used as a thickener is too large, the high-rate charge / discharge characteristics may be deteriorated, or the viscosity of the coating solution may become extremely high, making coating difficult.

  As the alumina hydrate, boehmite is preferably used from the viewpoint of easily obtaining thermal stability and liquidity suitable for coating.

  Various latexes such as styrene-butadiene latex can be used as the aqueous dispersible resin, and the addition amount is preferably 2% by mass or more and 15% by mass or less with respect to the alumina hydrate. From the point of balance of powder fall of the coating layer and voids in the coating layer, 3% by mass or more and 10% by mass or less is more preferable.

(Nonaqueous electrolyte secondary battery separator)
The non-aqueous electrolyte secondary battery separator of the present invention can be obtained by coating a non-aqueous electrolyte secondary battery separator coating liquid on a nonwoven fabric and drying it.

  Examples of the method for producing the nonwoven fabric used for the non-aqueous electrolyte secondary battery separator of the present invention include a spunbond method, a melt blow method, a dry method, a wet method, an electrospinning method, and the like, but are limited to these production methods. Is not to be done. In addition, for the purpose of controlling the flatness and thickness of the nonwoven fabric surface, it is possible to perform a calendar process or a thermal calendar process. Nonwoven materials include polyethylene terephthalate, polybutylene terephthalate and derivatives thereof, polyesters such as aromatic polyester and wholly aromatic polyester, polyolefin, acrylic, polyacetal, polycarbonate, aliphatic polyketone, aromatic polyketone, aliphatic polyamide, aromatic Polyamide, wholly aromatic polyamide, polyimide, polyamideimide, polyphenylene sulfide, polybenzimidazole, polyetheretherketone, polyethersulfone, poly (para-phenylenebenzobisthiazole), poly (para-phenylene-2,6-benzo Fibers made of resins such as bisoxazole), polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, polyurethane, and polyvinyl chloride Cellulose fibers listed beauty, it is also possible to use two or more kinds as the material.

  The nonwoven fabric used for the non-aqueous electrolyte secondary battery separator of the present invention preferably has a basis weight of 5.0 to 30.0 g / m 2. If the basis weight exceeds 30.0 g / m 2, the nonwoven fabric occupies most of the separator, and the effect of the coating layer may be difficult to obtain. If it is less than 5.0 g / m2, it may be difficult to obtain uniformity as a nonwoven fabric. The basis weight of the nonwoven fabric is more preferably 7.0 to 20.0 g / m2. The basis weight means the basis weight based on the method defined in JIS P 8124 (paper and paperboard—basis weight measurement method).

  There is no particular limitation on the method for coating the non-aqueous electrolyte secondary battery separator coating liquid on the nonwoven fabric. For example, conventionally known air doctor coater, blade coater, knife coater, rod coater, squeeze coater, impregnation coater, gravure coater Kiss roll coater, die coater, reverse roll coater, transfer roll coater, spray coater and the like. The adhesion amount of the coating layer is preferably 1.0 to 20.0 g / m2, and more preferably 4.0 to 15.0 g / m2. If the amount of the coating layer deposited is less than 1.0 g / m 2, the surface of the nonwoven fabric cannot be sufficiently covered, the pore diameter becomes large, and short-circuiting may not be achieved and good battery characteristics may not be exhibited. . On the other hand, when the adhesion amount of the coating layer exceeds 20.0 g / m 2, it may be difficult to reduce the thickness of the separator, or the large current charge / discharge characteristics of a battery using the separator may be deteriorated. Moreover, an antifoamer, a wetting agent, etc. can be suitably added in a coating liquid as needed.

  The method of drying after coating is not particularly limited, and a known drying method can be used. In particular, a method of drying by heating such as a method of blowing hot air or a method of irradiating infrared rays is preferably used because of its good productivity. It is done.

  In the present invention, the basis weight of the nonaqueous electrolyte secondary battery separator is preferably 6.0 to 50.0 g / m 2, and more preferably 15.0 to 40.0 g / m 2. Moreover, 10.0-50.0 micrometers is preferable and, as for the thickness of a separator, 15.0-40.0 micrometers is more preferable. The density of the separator is preferably 0.4 to 1.2 g / cm 3, and more preferably 0.6 to 1.0 g / cm 3. In addition, after coating and drying, calendering can be performed for the purpose of controlling the flattening and thickness of the coating layer surface.

<Example>
EXAMPLES Hereinafter, although the Example and comparative example of this invention are shown and demonstrated in detail, this invention is not limited to this description at all.

<Measurement of mass ratio of mass of filtration residue to dry mass of carboxymethyl cellulose (water-soluble dispersant and / or thickener) dissolved in aqueous solution>
Two liters of an aqueous solution containing 0.3% by mass of carboxymethylcellulose or a salt thereof (% by mass based on the dry mass of carboxymethylcellulose or a salt thereof) was prepared. Two liters of this aqueous solution was filtered with a 250 mesh filter (stainless steel, opening 63 μm) using a filter (“Separoto” manufactured by Kiriyama Seisakusho) under a reduced pressure condition of −200 mmHg. The residue remaining on the 250 mesh filter was blown and dried at a temperature of 105 ° C. for 16 hours, and then the weight of the dried residue was measured and expressed as a mass ratio (ppm) to the mass of carboxymethyl cellulose in the carboxymethyl cellulose solution. .

<Measurement of maximum particle size, average particle size and particle size distribution>
The maximum particle size, average particle size, and particle size distribution of carboxymethyl cellulose or a salt thereof were measured using a laser diffraction / scattering particle size distribution meter (Microtrac Model-9220-SPA, manufactured by Nikkiso Co., Ltd.). Here, the maximum particle size is a value of a volume cumulative 100% particle size, and the average particle size is a value of a volume cumulative 50% particle size. In measurement, the sample was placed in methanol and stirred and dispersed, and then the measurement was performed.

<Production of non-woven fabric>
45 parts by mass of oriented crystallized polyethylene terephthalate (PET) short fibers having a fineness of 0.06 dtex (average fiber diameter of 2.4 μm) and a fiber length of 3 mm, an orientation of fineness of 0.1 dtex (average fiber diameter of 3.0 μm) and a fiber length of 3 mm 15 parts by mass of crystallized PET-based short fibers, a fine component of 0.2 dtex (average fiber diameter 4.3 μm), and a fiber length of 3 mm PET-based short fibers for a single-component binder (softening point 120 ° C., melting point 230 ° C.) 40 parts by mass Were mixed together, disintegrated in water with a pulper, and a uniform papermaking slurry having a concentration of 1% by mass was prepared under stirring by an agitator. Thereafter, this papermaking slurry was made up by a wet type using a circular paper machine, and the nonwoven fabric strength was expressed by bonding the PET short fibers for binder with a cylinder dryer at 120 ° C., with a basis weight of 15.2 g / m 2. A non-woven fabric was used. Furthermore, this nonwoven fabric was subjected to heat treatment at a roll temperature of 185 ° C., a linear pressure of 740 N / cm, and a conveying speed of 20 m / min using a 1-nip thermal calendar composed of a metal roll and a metal roll. Produced.

<Example 1>
180 parts by mass of water, alumina hydrate (boehmite, single particle, average particle size 0.9 μm, specific surface area 5.5 m 2 / g, aspect ratio 2.5, manufactured by Naval Tech Co., Ltd., trade name: APYRAL (registered trademark) AOH60 ) As a water-soluble dispersant, the viscosity ratio at 25 ° C. of the 1% by weight aqueous solution is 100 mPa · s, the degree of etherification is 0.65, and the volumetric cumulative 100% particle diameter is 49 μm. A disperser equipped with a saw blade type blade with 20 parts by mass (0.4 parts by mass as a solid content) of a 2% by mass aqueous solution of 8 ppm carboxymethylcellulose sodium salt (hereinafter referred to as “CMC-Na”). Used, mixed, stirred, and then used as a thickener, a 1 mass% aqueous solution at 25 ° C. with a viscosity of 5000 mPa · s, a degree of etherification of 0.7, and a volume cumulative 100% particle The mass ratio (the amount of filtration residue) of 45 ppm was mixed with 80 parts by mass (0.8 parts by mass as a solid content) of the CMC-Na aqueous solution and stirred, and then the solid content was 48% by mass. 18.75 parts by mass (9 parts as solid content) of styrene-butadiene latex was mixed and stirred, and further, ion-exchanged water was added to adjust the concentration, so that the nonaqueous electrolyte secondary battery had a solid content concentration of 25 mass%. A separator coating solution was prepared.

  The coating solution is uniformly applied to one side of the nonwoven fabric and dried so as to have a dry solid content of 10 g / m2 with a gravure coater on the nonwoven fabric after the thermal calendering treatment, and a lithium ion battery separator having a thickness of 30 μm is obtained. Obtained.

<Comparative Example 1>
180 parts by mass of water, alumina hydrate (boehmite, single particle, average particle size 0.9 μm, specific surface area 5.5 m 2 / g, aspect ratio 2.5, manufactured by Naval Tech Co., Ltd., trade name: APYRAL (registered trademark) AOH60 ) As a water-soluble dispersant, the viscosity ratio at 25 ° C. of the 1 mass% aqueous solution is 100 mPa · s, the degree of etherification is 0.65, the volume cumulative 100% particle diameter is 150 μm, and the mass ratio (filtration A disperser provided with 20 parts by weight (0.4 parts by weight as a solid content) of a 2% by weight aqueous solution of 150 ppm carboxymethylcellulose sodium salt (hereinafter referred to as “CMC-Na”) with a saw blade type blade. Used, mixed, stirred, and then used as a thickener, a 1 mass% aqueous solution having a viscosity of 5000 mPa · s at 25 ° C., a degree of etherification of 0.7, a total volume of 100 80 parts by mass (0.8 parts by mass as a solid content) of a 1% by mass aqueous solution of CMC-Na having a particle size of 150 μm and a mass ratio (filtration residue amount) of 150 ppm was mixed and stirred. 18.75 parts by mass (9 parts as a solid content) of styrene-butadiene latex of mass% is mixed and stirred, and further, ion-exchanged water is added to adjust the concentration, and the non-aqueous electrolyte with a solid content concentration of 25 mass% is adjusted. A coating solution for the next battery separator was prepared.

  The coating solution is uniformly applied to one side of the nonwoven fabric and dried so as to have a dry solid content of 10 g / m2 with a gravure coater on the nonwoven fabric after the thermal calendering treatment, and a lithium ion battery separator having a thickness of 30 μm is obtained. Obtained.

[Coating properties]
The coating liquid obtained in each Example and each Comparative Example was applied to the nonwoven fabric laid on the black drawing paper with a manual rod coater that gave a coating amount of 10 g / m 2 after drying. When the nonwoven fabric was removed from the drawing paper, the trace of the coating liquid adhering to the drawing paper was observed and evaluated according to the following degree.
○: No trace of coating liquid on drawing paper.
Δ: There is a trace of the coating liquid that breaks through at a frequency of 1 piece / cm 2 or less.
X: There is a trace of the coating liquid that has betrayed at a frequency exceeding 1 piece / cm 2.

  As shown in the Examples and Comparative Examples, the nonaqueous electrolyte secondary battery separator coating solution using the water-soluble dispersant and / or thickener within the scope of the present invention has few defects during coating. The occurrence of streaks can be suppressed, and a uniform conductive coating film can be formed. Therefore, a secondary battery separator with little reduction in capacity can be obtained even when charging and discharging are repeated. On the other hand, Comparative Example 1 that does not satisfy the scope of the present invention has many defects during coating, and the effects of the present invention cannot be obtained.

Claims (5)

  Carboxymethyl cellulose or a salt thereof used as a water-soluble dispersant for a non-aqueous electrolyte secondary battery separator, and 100% cumulative volume measured by a laser diffraction / scattering particle size distribution meter using methanol of the carboxymethyl cellulose as a dispersion medium 2 liters of a 0.3% by weight aqueous solution of the carboxymethylcellulose or a salt thereof having a particle diameter of less than 50 μm and a dry weight of B are prepared and filtered through a 250 mesh filter under a reduced pressure condition of −200 mmHg. Carboxymethylcellulose or a salt thereof, wherein the ratio of the dry mass A to the dry mass B is less than 50 ppm when the dry mass A of the residue on the filter is measured.   A coating solution for a non-aqueous electrolyte secondary battery separator containing the carboxymethyl cellulose or a salt thereof according to claim 1, alumina hydrate, and a water-dispersible resin.   A coating solution for a non-aqueous electrolyte secondary battery separator containing the carboxymethyl cellulose or a salt thereof, an alumina hydrate, a water-dispersible resin, and a thickener according to claim 1.   The thickener is carboxymethylcellulose or a salt thereof, and 100% cumulative volume particle diameter measured by a laser diffraction / scattering particle size distribution meter using methanol of the carboxymethylcellulose as a dispersion medium is less than 50 μm, and a dry mass of B Two liters of a 0.3% by mass aqueous solution of the carboxymethylcellulose or a salt thereof was prepared and filtered through a 250 mesh filter under a reduced pressure condition of −200 mmHg, and the dry mass A of the residue on the filter after filtration was measured. In this case, the ratio of the dry mass A to the dry mass B is less than 50 ppm. The coating solution for a nonaqueous electrolyte secondary battery separator according to claim 3.   A lithium ion battery separator, wherein the coating liquid according to any one of claims 2 to 4 is applied to a nonwoven fabric and dried.